Setting the $boolean value to true (1) will cause the node value of the $tree object passed into visit to be set with the root value found in the $array_tree. Setting it to false (0), or not setting it, will result in the first value in the $array_tree creating a new node level.

This method accepts a CODE reference as its $filter_function argument and throws an exception if it is not a code reference. This code reference is used to filter the tree nodes as they are created, the $filter_function is passed the node value extracted from the array prior to it being inserted into the tree being built. The $filter_function is expected to return the value desired for inclusion into the tree.

This method is used to set the $array_tree that our Tree::Simple hierarchy will be constructed from. It must be in the following form:

[
'Root', [
'Child1', [
'GrandChild1',
'GrandChild2'
],
'Child2'
]
]

Basically each element in the array is considered a node, unless it is an array reference, in which case it is interpreted as containing the children of the node created from the previous element in the array.

The tree is validated prior being accepted, if it fails validation an exception will be thrown. The rules are as follows;

The root node is validated against this in this function, but all subsequent nodes are checked as the tree is built. Any nodes found to be array references are rejected and an exception is thrown. If you desire your node values to be array references, you can use the node filtering mechanism to achieve this as the node is filtered after it is validated.

This is the method that is used by Tree::Simple's accept method. It can also be used on its own, it requires the $tree argument to be a Tree::Simple object (or derived from a Tree::Simple object), and will throw and exception otherwise.